The present invention relates to a breeding method of a female pig for propagation and a feed for a female pig for propagation. More specifically, the present invention relates to a breeding method of a female pig for propagation for elevating a propagation result of a pig by further increasing a litter size, elevating the number of delactation, shortening the days of returning estrtus and allowing an annual average delivery frequency to grow, and a feed for a female pig for propagation which is suitably used in this breeding method.
So-called lipids such as triglycerides and fatty acids are excellent particularly as an energy source among three essential nutrients and have so far widely been used for a feed for livestock (refer to, for example, ┌Animal Dietetics┘ H. Morimoto, Yokendo, 1987). Among them, triglyceride is not isolated in the form of triglyceride and fed in almost all cases in the form of a material itself containing a lot of triglycerides such as soybean, rapeseed, corn, cotton seed and rice bran or cakes containing triglycerides obtained after pressing oils from the above materials (┌Japan Standard Feed Component Table┘ edited by an executive office of Fisheries Technology Conference in Ministry of Agriculture and Fisheries, Japan Livestock Industry Association, 1995). In recent years, fatty acids obtained by hydrolyzing this triglyceride, particularly hardened fatty acids such as beef tallow and palm oil tend to be used in many cases because of easiness in handling.
These triglycerides and fatty acids have been used blending with general mixed feeds for the purpose of efficiently supplying energy and have not been used for the purpose of improving a breeding efficiency paying attentions to a physiological activity of a specific fatty acid. With respect to this point, only evaluation of fat and oil raw materials and fats and oils as energy sources such as a digestible nutrient total amount and metabolizable energy is described in the Japan Standard Feed Component Table described above which is a leading standard book of livestock nutrient in our country.
On the other hand, fatty acid calcium salt which is one of lipids is a relatively new material which came to be first used as a feed in 1980s. This fatty acid calcium salt is widely used as a high energy feed for livestock such as high yielding dairy cows and others, particularly for supplying energy in a hot weather (refer to, for example, ┌Utilization Data of Fat and Oil to Cow Feed┘ The National Federation of Dairy Cooperative Associations, 1988). Further, known as other uses are a method in which this fatty acid calcium salt is used for supplying energy which is liable to be short when feeding mainly grass for a growth in rumen in breeding beef cattles, whereby a healthy growth in rumen and a good grown body are obtained (┌Beef Cattle Journal, February issue, March issue, July issue, August issue and September issue┘ T. Terada, 1997), a method in which calcium salt of fatty acid contained in fish oil is fed to cattles and pigs to introduce eicosapentaenoic acid and docosahexaenoic acid into meats (Japanese Patent Application Laid-Open No. 289734/1996), a method in which calcium salt of fatty acid contained in linseed oil is fed to milking cows to introduce xcex1-linolenic acid into milk (┌Nicchiku Report┘ vol. 66, No. 10, p. 889 to 897, S. Ishida et al., 1995) and a method in which calcium salt of fatty acid contained in linseed oil is fed to egg breed chickens to introduce xcex1-linolenic acid into eggs (Japanese Patent Application Laid-Open No. 315350/1994).
As described above, all of a triglyceride, a fatty acid and fatty acid calcium salt have so far widely been used as a raw material for a feed, and they have been used in almost all cases for the purpose of (1) growing a body and improving production of milk by efficiently supplying energy or (2) introducing some kinds of fatty acids into livestocks such as beef, milk, pork, chickens and eggs.
In recent years, attentions are paid to a physiological activity of unsaturated fatty acids such as linoleic acid, linolenic acid, eicosapentaenoic acid and docosahexaenoic acid as new uses of these lipids, and it is tried to make use of them for breeding of cattles (┌Clinical Veterinary┘ vol. 14, No. 7, p. 33 to 39, M. Nishikai, 1996; Feetstuffs, Staples, C. R. et al., Jan. 12, 1998). Further, it is reported that these unsaturated fatty acids reduce a death rate of fertilized ovums, which results in elevating a fecundation rate of cattles (Thatcher, W. W. et al., J. Anim. Sci., 72 (Suppl. 3), p. 16 to 30, 1994).
As described above, researches regarding a relationship of a breeding result with triglycerides, fatty acids and derivatives thereof and applications thereof in breeding cattles have come to be carried out, but it is the existing situation that a relationship thereof with triglyceride, fatty acids and derivatives thereof in breeding pigs have not yet been researched. That is, as far as breeding of pigs is concerned, it has so far actively been tried to elevate an ability intrinsic to pigs by breeding based on a thremmatological method, and a litter size per head of a mother pig has come to reach, for example, 12 head/parturition on an average. However, it has not yet been tried to elevate a breeding result thereof from the viewpoints of nutrients such as feed components and physiologically active substances contained in feeds.
In light of the circumstances described above, an object of the present invention is to provide a breeding method of a female pig for propagation for elevating a breeding result of pigs by (1) increasing a litter size, (2) elevating the number of delactation, (3) shortening the days of returning estrus and (4) increasing an annual average delivery frequency. A second object thereof is to provide a feed for a female pig for propagation which is suitably used in this breeding method.
Thus, intensive researches repeated by the present inventors in order to achieve the objects described above have resulted in finding that the first object can be achieved by feeding a female pig for propagation with a lipid comprising a fatty acid having a prescribed carbon number in which a melting point and an iodine value each fall in a specific range and which has plural double bonds in a molecule and triglyceride and a metal salt thereof and that the second object can be achieved by a feed containing the lipid described above in a specific proportion. The present invention has completed based on such knowledge.
That is, the first object of the present invention can be achieved by a breeding method of a female pig for propagation characterized by feeding a feed comprising at least one lipid selected from a fatty acid having 12 to 24 carbon atoms which has a melting point falling in a range of xe2x88x9260 to 40xc2x0 C. and an iodine value falling in a range of 30 to 470 and which has 2 to 6 double bonds in a molecule, a triglyceride containing the above fatty acid and a metal salt of the above fatty acid, particularly a feed containing a lipid comprising a metal salt of the above fatty acid and, if necessary, a triglyceride containing the above fatty acid.
Further, the second object thereof can be achieved by a feed for a female pig for propagation characterized by comprising at least one lipid selected from a fatty acid having 12 to 24 carbon atoms which has a melting point falling in a range of xe2x88x9260 to 40xc2x0 C. and an iodine value falling in a range of 30 to 470 and which has 2 to 6 double bonds in a molecule, a triglyceride containing the above fatty acid and a metal salt of the above fatty acid in a proportion of 0.5 to 10% by weight in terms of the fatty acid described above.
In the breeding method of a female pig for propagation of the present invention (hereinafter referred to merely as ┌the breeding method of the present invention┘), fed with a female pig for propagation is at least one lipid selected from an unsaturated fatty acid, a triglyceride containing the above fatty acid and a metal salt of the above fatty acid.
Used as the unsaturated fatty acid described above is a fatty acid having 12 to 24 carbon atoms which has a melting point falling in a range of xe2x88x9260 to 40xc2x0 C., preferably xe2x88x9250 to 0xc2x0 C. and an iodine value falling in a range of 30 to 470, preferably 150 to 470 and which has 2 to 6 double bonds in a molecule. Capable of being preferably given as such fatty acid is at least one selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid.
Shown in Table 1 are the carbon numbers, the double bond numbers, the melting points and the iodine values of the respective fatty acids.
The preceding respective fatty acids given as examples can be obtained by hydrotically treating plant oils such as, for example, soybean oil, rapeseed oil, corn oil, safflower oil, sunflower oil, rice oil, beefsteak plant oil, evening primrose oil, borage oil and linseed oil, fish oils obtained from oceanic bonito, mackerel, sardine and tuna and fats and oils such as triglycerides originating in various microorganisms such as Conidiobolus genus of Entomophthorales. sp., Entomophthora genus, Mucor. sp. and Mortierella genus.
The fats and oils described above can be given as triglycerides containing the above fatty acids. Among these fats and oils, preferably used in the present invention are those having high contents of linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid.
On the other hand, the metal salts of the above fatty acids are suitably calcium salts and magnesium salts of the various fatty acids described above, and they may be used alone or in combination of two or more kinds thereof. A production process of the metal salts of these fatty acids shall be explained later in details.
The breeding method of the present invention is preferably applied to female pigs bleeded by artificial insemination, and a feeding amount per day of at least one fatty acid selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid falls usually in a range of 20 to 200 g, preferably 30 to 180 g. The preceding feeding amount of less than 20 g does not allow the effects of these fatty acids to be sufficiently exhibited. On the other hand, the amount fed in excess of 200 g does not provide more effects and allows an adverse effect exerted by excess energy to grow large.
In the present invention, preferably used as the lipid described above are those containing at least one fatty acid selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid in a proportion of 20 to 99% by weight. If this content is less than 20% by weight, a large amount of the lipid has to be fed in order to feed at least one fatty acid selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid in an amount of 20 g or more per day. As a result thereof, the breeding efficiency is likely to be reduced because of a problem of excess growth brought about by excess energy, and a content of the other nutrients (carbohydrates, proteins and the like) is likely to be relatively reduced.
The triglycerides and fatty acids described above are liquid at a room temperature if linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid or eicosapentaenoic acid is contained in a proportion of 20% by weight or more, but fatty acid calcium salts and fatty acid magnesium salts are solid. In terms of easiness in handling and easiness in admixing with a feed, these fatty acid metal salts are preferred among the lipids. In particular, solid powdery or granular fatty acid calcium salts and fatty acid magnesium salts are preferably used.
In the present invention, the triglycerides, fatty acids or fatty acid metal salts described above can be used in a mixture with conventional base feeds. Feeds which are usually available in the market for female pigs for propagation or fatting, for example, a feed having the following blending composition can be used as the base feed:
A blending proportion of the base feed to at least one lipid selected from the fatty acids described above, the triglycerides thereof and the metal salts of the above fatty acids is preferably decided so that at least one selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid is contained in a feed taken by a head per day in an amount of 20 to 200 g in terms of the fatty acid described above. In this case, the contents of linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid or eicosapentaenoic acid contained in both of the base feed and the above lipid have to be considered, and they are controlled by the following method.
First of all, when the base feed is compounded with soybean, soybean cake, powdered blood and fish meal, there is a possibility that linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid are contained as well in them, so that these base feeds are treated in advance with a solvent of chloroform/methanol=2/1 to extract a lipid fraction, and this fraction has to be analyzed by a gas chromatography to determine a content of at least one selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid. Secondly, linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid which are contained in the lipid described above are added to linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid which are contained in this base feed to control the feeding amount so that the feeding amount comes to 20 to 200 g per day in terms of the fatty acid described above.
The feed intake amount per day is different depending on the breed of a pig used and falls in a range of about 2 to 4 kg per head. Considering, for example, a case where the feed intake amount is set at about 3.5 kg/day/head, it is assumed that analysis of the base feed described above shows a linoleic acid content of 10 g in 3.5 kg of the base feed. Accordingly, in this case, the lipid corresponding to 10 to 190 g of linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid or eicosapentaenoic acid has to be added. Thus, blending 20 to 380 g of soybean oil having a linoleic acid content of 50% by weight with this base feed results in providing a feed having the intended composition. This feed may be used in the form of powder obtained merely by blending, a so-called mash type or may be used in a pelletized form obtained by means of a suitable extrusion-molding machine.
In the breeding method of the present invention, a duration of feeding female pigs with the feed described above extends from 30 days before artificial insemination up to 3 weeks after the artificial insemination. That is, the feed comprising the lipid containing at least one fatty acid selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid is fed in a duration extending from 30 days before artificial insemination up to 3 weeks after the artificial insemination. In this case, the feed is preferably fed in a proportion of 2 to 4 kg per head a day and 20 to 200 g per head a day in terms of the fatty acids described above. In the present invention, an amount corresponding to the amount achieved by feeding the feeding amount described above every day in the duration described above may be fed in any period in the duration described above, but taking the effects of the present invention into consideration, the amount described above is preferably fed every day in the duration described above. When the desired feeding amount is not achieved in the duration described above, the breeding result-improving effect becomes unsatisfactory, and therefore it is not preferred. In the present invention, the feed is preferably fed so that the total amount of the above fatty acid reaches 1500 to 9000 g per head.
The present invention provides a feed for a female pig for propagation (hereinafter referred to merely as ┌the feed of the present invention┘).
The feed of the present invention comprises at least one lipid selected from a fatty acid having 12 to 24 carbon atoms which has a melting point falling in a range of xe2x88x9260 to 40xc2x0 C., preferably xe2x88x9250 to 0xc2x0 C. and an iodine value falling in a range of 30 to 470, preferably 150 to 470 and which has 2 to 6 double bonds in a molecule, a triglyceride containing the above fatty acid and a metal salt of the above fatty acid in a proportion of 0.5 to 10% by weight in terms of the fatty acid described above.
In the feed of the present invention, the fatty acid described above and the like have a content falling preferably in a range of 1 to 8% by weight, particularly suitably 1.1 to 6% by weight in terms of the fatty acid from the viewpoint of effectively feeding the feed. Preferably used as this fatty acid is at least one selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid.
Calcium salts and magnesium salts of the above fatty acids are preferred as the fatty acid metal salt. In particular, suited are fatty acid calcium salt and fatty acid magnesium salt containing at least one selected from linoleic acid, linolenic acid, bishomo-xcex3-linolenic acid, arachidonic acid and eicosapentaenoic acid in a proportion of 20 to 99% by weight. They may be used alone or in combination of two or more kinds thereof.
Among the lipids described above, these fatty acid metal salts are suited in terms of easiness in handling and easiness in admixing with the feed.
In the feeds of the present invention, particularly suited is the feed produced by blending the base feed with a metal salt of at least one fatty acid obtained by decomposing or refining soybean oil, corn oil, rapeseed oil, sunflower oil, safflower oil, sesame oil, rice oil, beefsteak plant oil, evening primrose oil, borage oil, linseed oil, palm oil or fish oil. Especially, preferred is the feed produced by blending a combination of the above metal salt with a triglyceride containing the fatty acid described above.
The metal salts of the fatty acids described above are produced by reacting the fatty acids with metal oxides or metal hydroxides, and preferred are those produced by means of an extruder having at least a raw material-feeding zone, a kneading and reacting zone and a cooling zone. Further, suited are those produced by controlling a temperature of the raw material-feeding zone in the extruder to 20 to 80xc2x0 C., a temperature of the kneading and reacting zone to 80 to 200xc2x0 C. and a temperature of the cooling zone to xe2x88x9220 to 5xc2x0 C.
The extruder described above is a pressure extruder having a raw material-feeding zone, a reacting zone and a cooling zone, and capable of being used are those of a single shaft type in which one rotating screw is inserted into a cylinder and a two shaft type in which two screws rotating in the same direction or different directions are inserted into a cylinder, and having a cross section of an 8 character type. In particular, the extruder of a two shaft type is preferably used in the present invention in terms of a kneading capacity. The screw in this extruder of a two shaft type is used by suitably combining plural parts which can usually carry out operations such as delivering, reversing and kneading.
The cylinder part of this extruder is divided into plural barrels corresponding to a raw material-feeding zone, a kneading and reacting zone and a cooling zone, and external jackets are installed in the circumferences of the respective barrels, wherein a specification which can meet both heating and cooling can be employed so that the jackets can be applied to any of the zones described above by each barrel.
In the present invention, a temperature of a raw material-feeding site in the raw material-feeding zone is maintained at 20 to 80xc2x0 C., preferably 30 to 70xc2x0 C., and fatty acid, metal oxide or metal hydroxide and water are introduced to control a temperature of a kneading and reacting site in the kneading and reacting zone is maintained at 80 to 200xc2x0 C., preferably 100 to 190xc2x0 C. to react them to form a fatty acid metal salt. Further, a cooling site in the cooling zone is maintained in a range of xe2x88x9220 to 5xc2x0 C., preferably xe2x88x9215 to 0xc2x0 C. for cooling, whereby the desired fatty acid metal salt is advantageously produced.